The Great Shremad Bhagwad Geeta cannot be expressed and translated by any human as the great words are God-self spoken by Lord Shree Krishna showing the path related to Karm,Ghyan and Bhakti.

In the above shlok from Shreemad Bhagwad Geeta Lord Shree Krishna is preaching Arjun and saying that he will come again and again to establish the Peace, Dharm,Ghyan and Knowledge or when ever sins or Adharm increases or when there is a need of it or when required by humble saint for the cause of humanity of the people.